The Program Project will support an interdisciplinary approach directed at several questions relating to: the potential for central nervous regeneration or reinnervation; the nature of environmental and hormonal influences upon the maturing nervous system; the degree of functional compensation that may occur after traumatic and other interference with neural connections. Ten individual projects are involved, with the emphasis being on the cerebral cortex and spinal cord, but including in vitro and in vivo studies of the fundamental mechanisms of synapse formation. The individual projects are concerned with (a) possible synaptic reorganization after selective deaffereniation of parts of the allocortex and of the red nucleus; (b) possible synaptic recorganization after selective fetal brain lesions and after neonatal malnutrition and endocrine disturbance; (c) the acute and chronic adaptive behavior of motor cortex neurons following experimetal production of the upper motor neuron syndrome; (d) the formation of connections in the genetically disturbed cerebral cortex; (e) functional modifications of the cerebral cortex following sensory deprivation or receptor damage: (f) plasticity of motor control by the cerebellum. The purpose of the proposal is to stimulate interaction and collaboration by the various investigators and to support shared facilities.